To accomplish this, scientists use a variety of evidence, from tree rings to the amounts of radioactive materials in a rock. Geodesy Geomagnetism Geophysical survey Seismology Tectonophysics. Main article: Radiocarbon dating.

The decay of radioactive materials can be shown with a graph Figure Uranium decays to form lead with a half-life of 4. These thick layers alternate with thin, clay-rich layers deposited during the winter. By measuring the carbon in organic material , scientists can determine the date of death of the organic matter in an artifact or ecofact.